The present invention is directed to a method and apparatus for the manufacture of optical transmission elements or optical waveguide conductors which have a fiber-shaped optical waveguide loosely received in a tubular jacket containing a filling material and having a diameter greater than the waveguide so that the waveguide is freely movable in the jacket to a certain extent.
An optical cable, which has a fiber-shaped optical waveguide loosely received in the interior of a tubular sleeve is disclosed in German A.S. 25 13 722. The tubular sleeve or jacket itself consists of two concentric layers, which are manufactured from different plastic materials and which accordingly exhibit different mechanical properties.
In the manufacture and processing of optical transmission elements or cables of this type, a series of difficulties occur which consist of the fact that a precise conformity of the mean length of the tubular jacket to the optical waveguide fiber must be guaranteed, or, however, that the optical waveguide fiber must have an excess length of a definite amount. Furthermore, cautions must be exercised so that during the introduction of a filling compound, the compound does not disturb the tubular jacket and the above mentioned relationship between the length of the fiber and the tubular jacket. Moreover, a subsequent length variation following the manufacturing process, which variation may occur either with an elastic post-shrinkage or due to an excessively large coefficient of thermal expansion, must be avoided.